docs: def _remove_trailing_new_line(l):
      """Remove a single instance of new line at the end of l if it exists.
  
      Returns:
          bytestring
      """
      # replace only 1 instance of newline
      # match longest line first (hence the reverse=True), we want to match "\r\n" rather than "\n" if we can
      for n in sorted(new_lines_bytes, key=lambda x: len(x), reverse=True):
          if l.endswith(n):
              remove_new_line = slice(None, -len(n))
              return l[remove_new_line]
      return l